1. Field of the Invention
The invention concerns a coating for a smoothing and/or polishing element, particularly a flexible grinding wheel, provided with a flexible abrasive insert, for smoothing and polishing stone material (marble, granite, sandstone, glass, ceramic, various agglomerates, and so on).
The invention further concerns a grinding wheel provided with a coating, a process for obtaining the same, as well as a process for realising the same.
2. Description of the Prior Art
At present, no solution exists in the abrasive field, as well as in the field of the relevant alloying elements, suitable to smooth the above materials, that allows one to obtain or use:
1) shaped grinding wheels for smoothing and polishing shaped profiles, frames, Greek key design, toroidal profiles;
2) grinding wheels for straight, cylindrical or rotative flat tool ribs;
3) plateau for polishing marble plates and similar;
4) rotative flat tools for polishing flat or convex ribs on marble and similar;
5) frankfurt sectors for band polishing machines;
6) cloths form or diapad sectors for flat or shaped surfaces, hand used of used by orbital honing machines; and
7) small plates, rotative flat tools or disks used with portable rotative or roto-orbital machines.
At present, the above mentioned tools are realised by the following technique, and employing, among the others, the following materials;
a) rigid binding grinding wheels with a rigid support;
b) magnesian binding with silicon carbide abrasive;
c) synthetic binding with silicon carbide abrasive;
d) synthetic binding with diamond abrasive;
e) resinoid binding with natural or synthetic diamond abrasive.
All the above raw materials have a rigid structure, so as they have to be moulded on a rigid support, not being consequently possible to guarantee the elasticity features that are nowadays necessary in most cases.
Another known technique is the one relevant to the grinding wheels with elastic rubber support, having elastic diamond cloths. By this kind of technique, a sufficiently flexible product is obtained, characterised by a rubber body having a diamond cloths insert, particularly used to work shaped profiles.
It is well known in the field that diamond cloths are cloths comprised of a textile base with an electrolytic or resinoid insert, having the diamond as abrasive element, with a thickness ranging from 0.6 and 1 mm, 0.5 tenths of which comprising the thickness of the cloth, the remainder being, as already said, comprised of an electrolytic or resinoid diamond spreading.
However, the above mentioned known techniques have some drawbacks, mainly when they are employed on shaped grinding wheels, destined to the working of toroidal shaped profiles, or of profiles having a different shape.
Problems encountered during the working can be individuated in the analyses of the various working phases providing a first step, in which a diamond grinding wheel comprised of a metallic body and insert with coarse grain sintered diamond treatment (usually 40/50 mesh), or electrodeposited, electrolytic (for marble) or with a sintered metallic binding (for granite), a second step employing a grinding wheel having the above features, but a more fine diamond granulometry, of about 170/200 mesh, that can vary according to the user choice.
The following steps provide the use of non-metallic grinding wheels.
The main problem faced is when the user works employing grinding wheels of the resinoid synthetic magnesian type.
Another kind of instrument presently used is comprised of shaped grinding wheels made up of synthetic or resinoid binding, with a traditional abrasive, such as silicon carbide and the like.
These grinding wheels, independently from the used abrasive, are characterised by a usually metallic inner insert, while the remaining parts are comprised of the above mentioned alloying elements materials.
The above problem is due to the incompatibility between these grinding wheels and the grinding wheel of the metallic type according to the previous working step.
In fact, it is very difficult to realise a profile exactly corresponding to the previous one, especially being within a few hundredths of a difference to have uniformity in polishing.
Thus, one is in the situation of working with resinoid synthetic grinding wheels in case of a deformed and scored profile, with the consequent unavoidable damaging of the same.
During the last few years, requests relevant to the shaped profiles are always becoming big problems, and present technologies do not allow to satisfy all the above requirements, as far as costs, time, finishing and polishing are concerned.
Summarising the above, synthetic and resinoid grinding wheels deforms and scores since they are comprised of soft alloying elements, grinding wheels having a rubber body with diamond cloths insert (gluing) do not deforms, but quickly destroy, since cloth, being subjected to an undue work, easily tears and unsticks from the body before having finished its standard wearing.
It is evident that cloths glued on a rubber body are a provisional solution in absence of a specific technology.
As far as the finishing is concerned, the user must retouch the profile by hand.